Tag Archives: rhinovirus

People are less likely to catch common cold if they’re already infected with influenza

Flu and the common cold are both respiratory illnesses, but they are caused by different viruses. It can be difficult to tell the difference between them based on symptoms alone because they have similar symptoms. In general, colds are usually milder than flu and are more likely to have a runny or stuffy nose while influenza (the flu) can have very serious associated complications.

A new study by scientists from the Medical Research Council-University of Glasgow Centre for Virus Research found that people were less likely to catch either influenza or a common cold-causing rhinovirus if they were already infected with the other virus. Understanding how these distinct viruses hinder each other could be useful to improve forecasting models that predict respiratory disease outbreaks and strategies for controlling disease spread.

It has been observed before that common cold infections appear to be less frequent in the influenza season and vice versa. The study, published in the journal Proceedings of the National Academy of Sciences, is the first study with enough samples to provide strong evidence for this interaction at both the population and individual level.

Samples from 44,230 cases of acute respiratory illness, in 36,157 patients, were tested for 11 types of respiratory viruses over nine years in NHS Greater Glasgow and Clyde. Using this data, the researchers found that 35% tested positive for a virus and, of those, 8% were co-infected with more than one type of virus. The study looked at how 11 viruses interacted and found relationships between some of the other virus pairs, but these were not consistent at both the individual host and population level, which the study did find for influenza A and rhinovirus.

The most striking interaction they found was between influenza A viruses and rhinoviruses, a type of virus that can cause the common cold. Computer modeling of the data found that the inhibitory interactions between influenza and rhinoviruses appeared to occur within individual people as well as at a population level. Patients with influenza A were approximately 70% less likely to also be infected with rhinovirus than were patients infected with the other virus types.

The first author of the paper, Dr Sema Nickbakhsh from MRC-University of Glasgow Centre for Virus Research at the University of Glasgow, said: “One really striking pattern in our data is the decline in cases of the respiratory virus rhinovirus, which is typically a mild common cold-causing virus, occurring during winter, around the time that flu activity increases. In the same way as lions and spotted hyenas compete for food resources in the Masai Mara, we believe respiratory viruses may be competing for resources in the respiratory tract. There are various possibilities we’re investigating, such as these viruses are competing for cells to infect in the body, or the immune response to one virus makes it harder for another unrelated virus to infect the same person.”

Viruses from the same species – for example, different strains of influenza – could be expected to compete or generate an overlapping immune response in the body, but the researchers say what makes these findings interesting is the interaction between completely different types of viruses.

Dr Pablo Murcia, who led the research, said: “Traditionally people have studied viruses in isolation – you study only flu or rhinovirus – but we’ve shown here that we need to also be studying these viruses together like it’s an ecosystem. My team are now doing experiments to try and understand how respiratory viruses, including influenza and rhinovirus, interact. If we understand how viruses interact and how certain viral infections may favor or inhibit each other, then maybe we can develop better ways to target viruses. Studying interactions between viruses could help to explain why different viruses circulate in different seasons or why they affect different age groups, and within the body why certain types of viruses infect different parts of the respiratory tract, like the nose or the lungs.”

An example of how these viruses could also affect each other’s spread at a population level is the scenario where a person infected with one virus is more likely to stay home and consequently not catch another virus. Limitations of the study include: 1) the correlations observed cannot show what is causing these interactions and 2) samples were only taken from people with symptoms of a respiratory infection, so it may not capture how the viruses behave in people who do not develop symptoms.

Common cold.

New research shows why some people get the common cold more easily

New research shows how different human cells respond to rhinovirus, the vector of the common cold. The results could help explain why some people are more susceptible to the disease than others.

Common cold.

Image credits Myriam / Pixabay.

Common colds, asthma attacks, and a host of other diseases associated with the respiratory tract share a common cause — rhinoviruses. However, not all people are made the same: some are more resistant to the pathogen, while others collapse into bed at the merest whiff of it.

In a bid to understand why, one team from the Yale University studied how key human cells respond to the pathogen.

Where’s the chicken soup?

To get to the bottom of things, the team worked with epithelial cells harvested from the nasal passages or lungs of healthy human donors. The team exposed both types of epithelial cells — kept in cultures under the same environmental conditions — to the virus.

Epithelial cells are a specialized type of cell that creates membranes and linings throughout the body. They’re usually the first bits to come into contact with pathogens, and, as such, possess traits that help them fight off bacteria and viruses. Rhinoviruses also have to contend with these cells when trying to infiltrate the body. Upon exposure to the bugs, epithelial cells lining our airways react to the threat, usually clearing it out of our systems before it gets a foothold and triggers symptoms. In some cases, however, this mechanism doesn’t seem to work: exposed to rhinoviruses, they fall mildly, or even seriously, ill.

The team reports that under business-as-usual scenarios, nasal cells have the more robust antiviral reaction among the two samples of cells. Further lab tests involved activation of the RIG-I pathway — a pattern-recognition network that the body uses to identify pathogens — in both types of sample cells so the team could see how each operated under emergency scenarios.

Upon activation of the RIG-I network, both cell types produced antiviral responses and beefed up their defenses against oxidative stress. Viral activity usually puts oxidative stress, a kind of chemical damage, on the cells they attack — so such a reaction should help them weather the invasion. Nasal cells showed the strongest antiviral response, while bronchial (deeper respiratory system) cells exhibited the strongest oxidative resistance of the lot.

Bronchi.

Image credits Pearson Scott Foresman.

Excellence comes at a cost, however: the team also found that cells can act against oxidative stress or viruses, but not both at the same time. This was particularly interesting as inhaled irritants — for example cigarette smoke or tree pollen — also generate oxidative stress on cells, the team explains.

Nasal cells exposed first to cigarette smoke and then to rhinoviruses were more vulnerable to the virus’ effects, the team reports.

“Your airway lining protects against viruses but also other harmful substances that enter airways. The airway does pretty well if it encounters one stressor at a time. But when there are two different stressors, there’s a tradeoff,” says lead researcher Ellen Foxman.

“What we found is that when your airway is trying to deal with another stress type, it can adapt but the cost is susceptibility to rhinovirus infection. [The cells] survive the cigarette smoke but can’t fight the virus as well. And the virus grows better.”

Foxman says their study underscores a mechanistic link between environmental exposure and our body’s ability to resist the common cold. The findings also help explain why smokers tend to be more susceptible to rhinovirus infections.

The team hopes their efforts will lead to the discovery of new strategies to combat respiratory viruses, which cause an estimated 500 million colds and 2 million hospitalizations in the United States per year.

The paper has been published in the journal Cell Reports.

common cold

Did the vaccine for the common cold just had to include all rhinoviruses? Why didn’t you say so!

common cold

Credit: Flickr user Allan Foster

The common cold might not be cancer, but it’s sure is annoying. In the United States alone, doctors estimate one billion cases of the cold are recorded. For decades, scientists have been trying to come up with a vaccine that would neutralise the sore throat and running nose causing disease which is primarily triggered by rhinovirus infection.

The problem is that there are over 100 identified rhinoviruses and making a vaccine against one virus is rendered useless because there’s a whole armada out there. A team of researchers at the Emory University School of Medicine think they know how to make a common cold vaccine work, though. Their solution is simple: make a vaccine with all the rhinoviruses you can carry.

The first common cold vaccine was made in the 1960s. Back then, researchers showed it was possible to vaccinate people and prevent them from getting sick when put in contact with the virus. It only worked against a single strand of rhinovirus, though — the one they also placed in the vaccine. The sheer number of rhinoviruses circulating all around us has made a lot of scientists abandon hope that a common cold vaccine is feasible.

[panel style=”panel-warning” title=”How to reduce the risk of getting a cold” footer=”source: CDC.gov”]- Wash your hands often with soap and water. f soap and water are not available, use an alcohol-based hand sanitizer. Viruses that cause colds can live on your hands, and regular handwashing can help protect you from getting sick.
– Avoid touching your eyes, nose, and mouth with unwashed hands
– Stay away from people who are sick [/panel]

Emory University researchers, however, applied a simple straightforward solution to a seemingly complicated problem. They made a mixture of 25 types of inactivated rhinovirus, then injected them in 25 mice. They also made a mixture of 50 types of such viruses and injected them in rhesus macaques.

In response to the vaccine, both mice and monkeys created antibodies which later proved to prevent the virus from infecting human cells cultured in a dish.

“We think that creating a vaccine for the common cold can be reduced to technical challenges related to manufacturing,” says Martin Moore, associate professor of pediatrics at Emory University School of Medicine.

“It’s surprising that nobody tried such a simple solution over the last 50 years. We just took 50 types of rhinovirus and mixed them together into our vaccine, and made sure we had enough of each one,” Moore says. “If we make a vaccine with 50 or 100 variants, it’s the same amount of total protein in a single dose of vaccine. The variants are like a bunch of slightly different Christmas ornaments, not really like 50 totally different vaccines mixed.”

The researchers, however, could not test to see whether the animals themselves got sick because there isn’t any reliable animal model for rhinoviruses. Instead, the next thing the researchers plan to do is start a clinical trial with human subjects, something which is deemed feasible considering the non-pathological nature of the common cold. And if the results are confirmed in humans, then millions of sore throats will be made much happier in those cold winter nights.

Findings appeared in Nature Communications.